Prosthetic hands with motor powered digits are known. For example, WO 2007/063266 describes a prosthesis with a mechanically operable digit that is moved by an electric motor. In the prosthesis of WO 2007/063266 the electric motor is located within the digit. Shortcomings with known prostheses having motor driven digits, such as the prosthesis of WO 2007/063266 are dealt with in WO2010/149967 which provides a method of controlling a mechanically operable digit to improve the grip of the digit upon an object. The present inventor has appreciated a further need to improve known prostheses having motor driven digits, such as the prostheses of WO 2007/063266 and/or WO2010/149967.